Crude Protein Calculator

The Kjeldahl method estimates protein content in food and feed samples by measuring nitrogen — and the Crude Protein Calculator converts those lab titration results into a protein percentage. Enter your titre value, blank titre value, NaOH normality, and sample weight, then select the appropriate protein conversion factor for your sample type (e.g., cereal, fish, meat) to get the crude protein percentage, along with nitrogen content and protein mass.

mL

Volume of NaOH used to titrate the sample

mL

Volume of NaOH used to titrate the blank

N

Normality of sodium hydroxide solution

g

Weight of the sample being analyzed

Jones' factor based on sample type

Results

Crude Protein Percentage

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Nitrogen Content

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Protein Mass

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Frequently Asked Questions

What is crude protein?

Crude protein is an estimate of the total protein content in a sample, calculated by measuring nitrogen content and multiplying by a conversion factor. It includes both true proteins and non-protein nitrogen compounds.

What is the Kjeldahl method?

The Kjeldahl method is a standard laboratory procedure for determining nitrogen content in organic compounds. It involves digestion, distillation, and titration steps to quantify nitrogen, which is then converted to protein content.

Why do we use different protein conversion factors?

Different food types have varying amino acid compositions and nitrogen content. Specific conversion factors (Jones' factors) provide more accurate protein estimates for different sample types like cereals, meat, or fish.

How accurate is the crude protein calculation?

The crude protein method provides a good estimate but may overestimate true protein content since it measures all nitrogen, including non-protein nitrogen compounds. It's widely accepted for nutritional labeling and feed analysis.

What is the significance of blank titre value?

The blank titre value accounts for any nitrogen contamination in reagents or equipment. Subtracting it from the sample titre value ensures accurate measurement of nitrogen from the sample only.

What does normality of NaOH mean?

Normality represents the concentration of sodium hydroxide solution used in titration. It indicates the number of equivalents of NaOH per liter of solution and is crucial for accurate nitrogen quantification.